Studying and optimization of TCO/metal/TCO multi-layers for large area c-Si solar cells

Among transparent electrode architectures, TCO/metal/TCO multilayers can deliver optical transparency and electrical conductivity that match or surpass those of single TCO films and ultrathin metal layers. In this work, tin-doped indium oxide (ITO) thin films were first optimized on large-area substrates (156 × 156 mm 2 ) by systematically varying the target-to-substrate distance, sputtering pressure, and applied RF power. We report an optimized 50-nm-thick ITO layer deposited at a target-to-substrate distance of 115 mm, which exhibited a thickness non-uniformity of ∼10%, along with a carrier mobility of 47 cm 2 V −1 s −1 , a carrier concentration of 2.60 × 10 20 cm −3 , and a resistivity of 9.24 × 10 −4 Ω cm. Subsequently, oxide/metal/oxide (OMO) transparent electrode configurations were optimized using the optimized ITO as the oxide layer, investigating different combinations of oxide thickness and metal (Ag and Al) thicknesses. Among the studied structures, we report the ITO/Ag/ITO (25/10/25 nm) stack demonstrated superior performance, achieving a low sheet resistance of 12 Ω sq −1 and a high transmittance of 82.5% at 550 nm. When integrated into front/back-contacted silicon heterojunction (FBC-SHJ) solar cells, the optimized OMO electrode improved device performance compared with the other reference electrodes. With respect to the optimized 50-nm-thick ITO electrode, the ITO/Ag/ITO (25/10/25 nm) structure shows clear improvements in device performance, with increases of 16 mV in V OC , 0.20 mA cm −2 in J SC , and 1.23% in FF. These gains represent an absolute efficiency improvement of 1.00%, leading to a maximum efficiency of 23.20%. Interestingly, when a much thinner Ag layer is used (ITO/Ag/ITO, 25/2/25 nm), the device performance drops noticeably efficiency of 16.20%. We report that increasing the Ag thickness to 10 nm, however, leads to a substantial recovery and enhancement, emphasizing how sensitive device performance is to the thickness of the metallic interlayer.